1. Field of the Invention
The present invention relates generally to the hydroprocessing of heavy hydrocarbon-containing feed streams. More particularly, the present invention relates to a method of converting unwanted components in the heavy feed, primarily to more valuable products, and partly to forms in which they can be easily removed, while, at the same time, substantially eliminating the plugging of the hydroprocessing reactors.
2. Description of Background Art
It is well known by those skilled in the art that during the hydroprocessing (e.g., hydrofining) of heavy hydrocarbon feed streams, the reactors used to process the streams can become plugged. Reactor plugging is undesirable since, among other things, it results in poor operability, impedes adequate conversion, and ultimately leads to unproductive reactor shutdown time.
Reactor plugging is typically ascribed to high concentrations of oil soluble decomposable hydrofining catalytic elements which, by way of illustration, can include Fe, Co or Mo present as naphthenates or other species. In this regard, by way of illustration, U.S. Pat. No. 4,724,069 discloses, in column 5, lines 1-3, that high concentrations, i.e., about 100 ppm and above, of the aforementioned elements should be avoided to prevent plugging of the reactor.
It has also been discovered that the heavy hydrocarbon feed inlet and/or product outlet of continuous flow reactor units are readily plugged during high conversion operations (e.g., 60 or more weight percent) at temperatures of about 780.degree. F. to about 800.degree. F., where a dual catalyst system including 96 wppm or more of molybdenum naphthenate and a solid nickel-molybdenum catalyst component supported on alumina was used. It is believed, in this case, that plugging results from the formation of various insoluble materials. The accumulation of deposits results in severe and/or irreversible plugs and, eventually, the shutdown of the continuous flow reactor unit.
One standard approach of mitigating the problem of reactor plugging utilizes a catalyst system which is devoid of the oil soluble decomposable catalytic elements. This type of catalyst system uses only the solid component, for example, nickel-molybdenum supported on alumina. While this catalyst system affords commercial operability with about 97 wt. % of a mixture of fresh and partially deactivated catalysts of various ages (the mixture henceforth called an equilibrium catalyst), about 3 wt. % of fresh catalyst is usually added to the reactor at regular frequent intervals. This fresh catalyst addition is required to maintain all catalytic activities and to minimize the formation of various undesired insoluble materials. However, it would be desirable to improve the process economics associated with this type of usually expensive fresh catalyst addition. Thus, partial or complete elimination/substitution of fresh catalyst addition--without sacrificing any desired catalytic activities, or compromising insoluble/sediment control or operability--by some alternative or complementary means would be more favorable.
There are a variety of known techniques for hydroprocessing hydrocarbon-containing feed streams. For instance, U.S. Pat. No. 4,724,069 describes a process for hydrofining a hydrocarbon-containing feed stream in the presence of a supported catalyst bearing a VI-B, VII-B, or VIII metal on alumina, silica, or silica-alumina. A naphthenate of Co or Fe is typically introduced, as an additive, with the charge oil.
U.S. Pat. No. 4,557,823 describes a hydrofining process wherein a hydrocarbon-containing feed stream is contacted with a catalyst composition including a support selected from alumina, silica and silica-alumina, and a promoter including at least one metal selected from Group VI-B, Group VII-B and Group VIII of the Periodic Table. A decomposable compound selected from a Group IV-B metal is introduced into the hydrocarbon-containing feed stream prior to contacting the stream with the catalyst composition.
U.S. Pat. No. 4,389,301 describes hydroprocessing in the presence of an added dispersed hydrogenation catalyst (typically ammonium molybdate) and added porous contact particles (typically FCC catalyst fines, alumina, or naturally occurring clay).
U.S. Pat. No. 4,352,729 describes hydrotreating in the presence of a molybdenum blue solution in polar organic solvent introduced with the hydrocarbon charge.
U.S. Pat. No. 4,298,454 describes the hydroconversion of a coal-oil mixture in the presence of a thermally decomposable compound of a IV-B, V-B, VI-B, VII-B, or VIII metal, preferably Mo.
U.S. Pat. No. 4,134,825 describes the hydroconversion of heavy hydrocarbons in the presence of an oil-soluble compound of IV-B, V-B, VI-B, VII-B, or VIII metal added to the charge, the compound being converted to a solid, non-colloidal form by heating in the presence of hydrogen.
U.S. Pat. No. 4,125,455 describes hydrotreating in the presence of a fatty acid salt of a VI-B metal, typically molybdenum octoate.
U.S. Pat. No. 4,077,867 describes the hydroconversion of coal in the presence of an oil-soluble compound of V-B, VI-B, VII-B, or VIII metal plus a hydrogen donor solvent.
U.S. Pat. No. 4,067,799 describes hydroconversion in the presence of a metal phthalocyanine plus dispersed iron particles.
U.S. Pat. No. 4,066,530 describes hydroconversion in the presence of (i) an iron component, and (ii) a catalytically active metal component prepared by dissolving an oil-soluble metal compound in the oil and converting the metal compound in the oil to the corresponding catalytically active metal component.
Thus, a method of hydrofining a heavy hydrocarbon-containing feed stream which substantially eliminates the plugging of the reactor, while, at the same time, provides favorable conversion, would be a significant contribution to the art.